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Revisión de los Sciuridae del Aragoniense y del Rambliense en la fosa de Calatayud-Montalbán = Revision of Aragonian and Ramblian Sciuridae in the Calatayud-Montalban Trench

1988; Naturalis Biodiversity Center; Volume: 87; Linguagem: Inglês

0375-7587

Gloria Cuenca‐Bescós,

Mollusks and Parasites Studies

The Sciuridae are the family of rodents that comprises all extant and fossil squirrels. In the Ramblian and especially in the Aragonian of the Tertiary basin of Calatayud-Montalban (Aragon, Spain) the remains of Sciuridae are relatively abundant. A major problem solved in this paper is the distinction of Ml and M2, both in the upper and the lower dentition. Traditionally, in the literature these elements are treated as a unit Ml,2. We managed to separate them, on the basis of the study of material of two extant species, Atlantoxerus getulus and Sciurus vulgaris. In our study of the fossil Sciuridae from the Calatayud-Montalban Basin 9 species were recognized, belonging to 6 genera: Heteroxerus rubricati, H. grivensis, Atlantoxerus idubedensis sp. nov., A. blacki, Aragoxerus ignis, Spermophilinus besana sp. nov., S. bredai, Freudenthalia daamsi sp. nov. y Palaeosciurus feignouxi. Aragoxerus and Freudenthalia are new genera. Atlantoxerus idubedensis sp. nov. is a small Atlantoxerus, similar to primitive Heteroxerus, and characterized by a reduced or absent anterior cingulum in M1, M2 and M3. Spermophilinus besana sp. nov. is the smallest Spermophilinus species known so far. In the lower teeth the anterolophid is separated from the protoconid by a deep furrow, and the entoconid is reduced or absent. Aragoxerus gen. nov. (tribe Xerini) contains only one species, A. ignis, formerly assigned to Heteroxerus. Although Aragoxerus is quite similar to Heteroxerus, its smaller size, simple dental pattern, absence of metaconule and anterior cingulum, and the lack of accessory ornamentations permit us to distinguish it as a separate genus. Freudenthalia gen. nov. is a monospecific genus of uncertain systematic position, tentatively placed in the tribe Sciurini. Freudenthalia daamsi sp. nov. is the only species of this genus. It is characterized by a metaloph completely fused to the protocone, a loop-shaped metaconule, and the absence of the entolophid. Within the genus Heteroxerus two pairs of names are synonimized: H. vireti is a synonym of H. rubricati; their size and dental morphology are very similar, both have an anterior cingulum in the lower molars, well-developed entolophid, and a metaloph, wich is either free or tends to fuse with the posteroloph. H.huerzeleri is synonimized with H. grivensis. Several authors suggested this synonymy already. Populations assigned to H. huerzeleri belong in some cases to H. rubricati, and in most cases to H. grivensis. All populations described previously as H. cf. huerzeleri belong to H. grivensis. The Sciuridae are a family of rodents with a morphologically stable dental pattern. Hardly any modifications take place during large periods of time, but sudden changes may cause the abrupt appearance and disappearance of species, such as Freudenthalia daamsi and Aragoxerus ignis. Se describen tres nuevas especies de Sciuridae fosiles en la fosa terciaria de CalatayudMontalban: Atlantoxerus idubedensis, Spermophilinus besana, y Freudenthalia daamsi, esta ultima es la unica especie del genero Freudenthalia, descrito junto con Aragoxerus como generos nuevos. La descripcion de estas nuevas formas esta en el contexto de una revision sistematica de las especies fosiles de Sciuridae de la Fosa. Por ello se revisan adernas los generos Heteroxerus, Atlantoxerus y Spermophilinus, dando como resultado que se pongan en sinonimia dos casos del genero Heteroxerus: H. vireti con H. rubricati y H. huerzeleri con H. grivensis. Se cree un nuevo genero Aragoxerus para la especie A. ignis que anteriormente se incluia dentro del genero Heteroxerus. La sucesion de los yacimientos con Sciuridae ensuperposicion estratigrafica nos ha permitido hacer algunas precisiones a la bioestratigrafia de las areas de Daroca y Calamocha establecida por autores anteriores.